This invention relates to new synthetic lubricant compositions having exceptional thermal stability.
U.S. Pat. Nos. 2,396,191; 2,936,320; 3,021,357; 3,637,501; 3,912,640; and 4,080,303 are illustrative of prior art attempts to formulate lubricants containing esters of aromatic polycarboxylic acids.
U.S. Pat. No. 3,637,501 describes neo-carbon containing polycarboxylic acid esters wherein the ester groups on the aromatic nucleus contain at least one carbon atom connected directly to four other carbon atoms.
The number of lubricant patents and the importance of changes in composition found in these patents is testimony to the difficulty of making blends capable of simultaneously meeting desired criteria.
Recent technology concerning uncooled or insulated internal combustion engines requires lubricants able to withstand ring reversal temperatures in excess of 6500.degree. F. (343.30.degree. C.). Internal combustion engine operation at temperatures of 900.degree. F. (482.2.degree. C.) is being investigated. Moreover, ceramic elements in internal combustion engines may require lubricants capable of operation at temperatures in excess of 1000.degree.0 F. (537.8.degree. C.) or even 1200.degree. F. (648.9.degree. C.).
Prior art lubricants generally embody molecular structures that are resistant to thermal degradation and oxidation. These structures often incorporate highly branched or hindered carbon atom chains.
Synthetic ester oils had been recognized as useful for high temperature lubricant applications. Moreover, certain classes of esters had been considered superior in thermal properties. For example, Stauffer Chemical Company trade literature for SDL-1.TM. Lubricant refers to " . . . an industry-wide consensus that polyol esters provide the best balance of high temperature stability . . . ".
The "high temperature stability" mentioned in the prior art did not contemplate extraordinary operating temperatures of 900.degree. F. (482.2.degree. C.) or more. These very high engine operating temperatures redefine high temperature operating requirements and necessitate entirely new lubricant formulations.
Conventional practice has been to enhance the performance of lubricants with additives such as rust inhibitors, metal deactivators, and etc. Unfortunately, these additives often solve one problem at the expense of creating another. It is desirable to develop lubricant rectification systems and methods of operating engines that do not require extensive use of additives with deleterious side effects.